Rex Tillerson testifies during a confirmation hearing. Kevin Lamarque/Reuters

The day before Trump’s inauguration, his pick for Secretary of State will likely be getting questioned under oath.

Lawyers for a landmark climate lawsuit , which claims the US government failed to protect future generations from the dangers of global warming, are scheduled to depose Rex Tillerson on January 19.

The suit was brought by a group of youth plaintiffs, who range in age from 9 to 20 years old. The kids argue that by failing to prevent climate change despite detailed knowledge of the threats it poses, the federal government is violating their rights to life, liberty and property. They seek a ruling that will compel the government to take action on climate change.

Although the youth plaintiffs sued the federal government, several fossil fuel industry groups legally intervened, voluntarily joining the defense’s side. That includes the American Petroleum Institute, an organization Tillerson has close ties with — he formally served as chairman and was a member of the board of directors.

Julia Olson, the lead attorney for the case, tells Business Insider that the plaintiffs’ questions for Tillerson will center around what Exxon and its scientists have known about climate change and for how long.

“In part it’s like, What did you know and when did you know it?” Olson says, “and the next part is, Once you knew it, what did you do with that information? What did you tell the government? And then, what are the things you did to keep our national energy policy and system dependent upon fossil fuels? And what role did you play with the government in critical decisions at different points to ensure that we did not transition away from fossil fuels, even though you knew it was necessary to preserve our climate system?”

These questions very similar to those Senator Tim Kaine posed during Tillerson’s confirmation hearing before the Senate Foreign Relations Committee on January 11.

Senator Tim Kaine listens to testimony by Rex Tillerson. Jonathan Ernst/Reuters

Tillerson refused to answer a question from Kaine about the degree to which Exxon’s scientists knew about fossil fuels’ role in climate change. Kaine’s questions referenced findings from two investigative reports from InsideClimate News and the LA Times , both of which suggested that Exxon knew about the dangers of global warming as early as the 1970s but covered up the data and intentionally spread misinformation about climate science.

When under oath in a federal lawsuit, Tillerson will likely have to be far more forthcoming than he was before the Senate. The information revealed could later plague him as Secretary of State — especially since California, New York, and Massachusetts are pursuing their own investigations into whether Exxon knowingly misled the public and its shareholders.

The timing of Tillerson’s deposition the day before Donald Trump’s inauguration is mostly due to the constraints of the confirmation hearing schedule and the timeline of the trial, Olson explained.

“We have a very short window of time to compile the evidence,” she says. “But what we have told council for the intervenor defendants is, we will take the deposition anytime during the last two weeks of January that is convenient for them.”

In November, a federal judge denied all motions to dismiss the climate case, clearing the way for it to go to trial. The federal government has to file its answer to the plaintiffs’ complaint on January 13th, which will put the evidence-gathering phase of the trial into full gear.

If Tillerson does become Donald Trump’s Secretary of State, a strange situation will arise in relation to the lawsuit: Tillerson will be considered part of the group of industry groups that intervened in the case, but will also be named as a member of the federal government, the original defendant.

That scenario, Olson says, shows there is no longer any separation between the government and the fossil fuel industry.

“I would say very clearly demonstrates the story that this case tells, which is that the United States government and the fossil fuel industry have worked together to keep a fossil-fuel–based energy system in place, and that has caused climate change and has threatened the lives of these plaintiffs and future generations and resulted in constitutional violations,” she says.

Julia Olson (left) with the youth plaintiffs of the federal climate lawsuit. Andrea Willingham/Our Chidren’s Trust

The case, she says, has become a prime illustration of the conflicts of interest that many opponents to Tillerson’s appointment have cited.

“The fact that these industry groups have really worked in conjunction with the federal government to betray entire generations of Americans by destabilizing our climate system should on its face disqualify him from holding that high of an office within our federal government,” Olson says.